U.S. patent application number 13/894612 was filed with the patent office on 2013-10-03 for method for producing lithium-based layers by cvd.
This patent application is currently assigned to Annealsys. The applicant listed for this patent is Annealsys, Commissariat A L'Energie Atomique Et Aux Energie Alternatives. Invention is credited to Philipp ACHATZ, Jean-Manuel DECAMS, Jean-Luc DESCHANVRES, Maria del Carmen JIMENEZ AREVALO, Lucie JODIN, Sylvain POULET.
Application Number | 20130260024 13/894612 |
Document ID | / |
Family ID | 44303388 |
Filed Date | 2013-10-03 |
United States Patent
Application |
20130260024 |
Kind Code |
A1 |
JODIN; Lucie ; et
al. |
October 3, 2013 |
METHOD FOR PRODUCING LITHIUM-BASED LAYERS BY CVD
Abstract
A method for forming by CVD a lithium-based layer, according to
which the lithium precursor is in liquid form in a mixture
containing a solvent and a Lewis base.
Inventors: |
JODIN; Lucie; (Nancy,
FR) ; ACHATZ; Philipp; (Grenoble, FR) ;
DECAMS; Jean-Manuel; (Montpellier, FR) ; DESCHANVRES;
Jean-Luc; (Meylan, FR) ; JIMENEZ AREVALO; Maria del
Carmen; (Grenoble, FR) ; POULET; Sylvain;
(Saint Victor De Cessieu, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Annealsys
Commissariat A L'Energie Atomique Et Aux Energie
Alternatives |
Montpellier
Paris |
|
FR
FR |
|
|
Assignee: |
Annealsys
Montpellier
FR
Commissariat A L'Energie Atomique Et Aux Energie
Alternatives
Paris
FR
|
Family ID: |
44303388 |
Appl. No.: |
13/894612 |
Filed: |
May 15, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/FR2011/052899 |
Dec 8, 2011 |
|
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|
13894612 |
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Current U.S.
Class: |
427/126.1 |
Current CPC
Class: |
H01M 10/052 20130101;
H01M 10/0562 20130101; C23C 16/40 20130101; C23C 16/4486 20130101;
H01M 4/0428 20130101; Y02E 60/10 20130101; C23C 16/308
20130101 |
Class at
Publication: |
427/126.1 |
International
Class: |
H01M 4/04 20060101
H01M004/04 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 9, 2010 |
FR |
10.60280 |
Claims
1. A method for forming by CVD a lithium-based layer using a liquid
mixture comprising adducts formed by the placing in solution of a
lithium precursor, in the presence of a Lewis base and a solvent,
the three entities being distinct.
2. The method for forming by CVD a lithium-based layer of claim 1,
wherein the liquid mixture is sprayed in the form of an aerosol,
and then evaporated.
3. The method for forming by CVD a lithium-based layer of claim 1,
wherein the layer is made of LiPON, LiSiPON, or
(Li,La)TiO.sub.3.
4. The method for forming by CVD a lithium-based layer of claim 1,
wherein the Lewis base is an amine, advantageously of TMEDA or
TMPDA type.
5. The method for forming by CVD a lithium-based layer of claim 1,
wherein the lithium precursor is an organometallic precursor,
advantageously an alkoxyde, a .beta.-diketonate or an amide.
6. The method for forming by CVD a lithium-based layer of claim 1,
wherein the solvent is a non-oxygenated aliphatic or aromatic
organic solvent such as toluene or octane, or an alcohol-type
oxygenated organic solvent, such as butanol or isopropanol.
7. The method for forming by CVD a lithium-based layer of claim 3,
wherein the phosphorus precursor and/or the nitrogen precursor also
appears in liquid form or in the form of a solution.
8. The method for forming by CVD a lithium-based layer of claim 7,
wherein the phosphorus precursor and/or the nitrogen precursor is
added to the liquid mixture containing the lithium precursor.
9. The method for forming by CVD a lithium-based layer of claim 1,
wherein the layer is formed on a 3D textured structure.
10. The method for forming by CVD a lithium-based layer of claim 1,
wherein the layer forms the electrolyte of a microbattery.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to the manufacturing of
thin-film batteries, with a high power density.
[0002] The targeted applications especially concern chip cards and
smart tags enabling to recurrently measure parameters by means of
miniaturized implants. Another important application relates to the
power supply of internal clocks and of microsystems. These
applications impose for all the layers necessary to the battery
operation to be manufactured with techniques compatible with
industrial methods of microelectronics.
[0003] In practice, film batteries are deposited on 3D substrates
to increase the active surface area without modifying the component
size. In this context, it is necessary to use conformal deposition
techniques enabling to precisely control the chemical composition
of the material since the active layers are highly sensitive to a
modification of their composition.
[0004] More specifically, the present invention relates to a CVD
method ("Chemical Vapor Deposition") for manufacturing a layer
containing lithium, such as LiPON ("Lithium Phosphorous
OxyNitride"), LiSiPON ("Nitrogen-incorporated Lithium
SilicoPhosphate"), or (Li,La)TiO.sub.3 (Lithium lanthanum
titanate), involving precursors contained in a liquid mixture
comprising a solvent and a Lewis base.
BACKGROUND
[0005] "All-solid" microbatteries, in the form of thin films, have
been widely described in prior art. The operating principle relies
on the insertion and the desinsertion (or
intercalation/deintercalation) of an alkaline metal ion or of a
proton in the positive electrode. The main systems use, as an ion
species, the lithium ion or Li.sup.+. All the microbattery
components (current collectors, positive and negative electrodes,
electrolyte, encapsulation) are in the form of thin layers obtained
by PVD ("Physical Vapor Deposition") or CVD.
[0006] The total thickness of the stack is on the order of 15
.mu.m.
[0007] Different materials may be used: [0008] the current
collectors are metallic and may for example contain Pt, Cr, Au, Ti,
W, Mo. [0009] the positive electrode may especially be formed of
LiCoO.sub.2, LiNiO.sub.2, LiMn.sub.2O.sub.4, CuS, CuS.sub.2,
WO.sub.yS.sub.z, TiO.sub.yS.sub.z, V.sub.2O.sub.5. According to the
selected materials, a thermal anneal may be necessary to increase
the crystallization of the films and their insertion properties.
Such is for example the case for lithium oxides. However, certain
amorphous materials do not require such a processing, while
allowing a high insertion of lithium ions. [0010] the electrolyte
must be a good ion conductor and electronic insulator. It generally
is a vitreous material containing phosphorus oxide, boron, lithium
oxides, or lithium salts. The electrolytes with the best
performance contain phosphate, such as LiPON ("Lithium Phosphorous
OxyNitride") or LiSiPON ("Nitrogen-incorporated Lithium
SilicoPhosphate"). Their composition will determine the electric
properties, and especially the nitrogen concentration, which
enables to increase the ion conductivity. [0011] the negative
electrode may be metallic lithium deposited by thermal evaporation,
a metal alloy containing lithium, or an insertion compound (SiTON,
SnN.sub.x, InN.sub.x, SnO.sub.2 . . . ). It should be noted that
there also exist microbatteries with no anode (called "Li free").
In this case, a metal layer blocking the lithium is directly
deposited on the electrolyte. The lithium then deposits on this
layer. [0012] the encapsulation aims at protecting the active stack
from the outer environment and specifically from humidity.
Different strategies may be used: encapsulation from thin layers,
co-laminated encapsulation, or cover encapsulation.
[0013] The research made in this field aims at increasing the power
density of microbatteries, and this, in different possible ways:
[0014] by increasing the performance of the materials; and/or
[0015] by increasing the thicknesses; and/or [0016] by performing
the depositions on 3D textured structures, which enables to
increase the active surface area of the battery.
[0017] This third way is that selected for the present invention,
which more specifically focuses on electrolyte deposition.
[0018] It is admitted that the PVD technique (physical vapor
deposition), a standard method for depositing materials for
microbatteries, is not adapted to depositions on 3D structures. It
is thus necessary to use alternative techniques such as CVD,
possibly plasma-enhanced (PE-CVD).
[0019] Thus, document US 2005/0016458 describes a device enabling
to form a thin layer LiPON-based electrolyte. It implements the
PE-CVD technique, and uses solid lithium precursors and solid or
liquid phosphorus precursors, which are heated in bubbling systems
in order to be evaporated. The nitrogen is incorporated into the
layer by means of a plasma present in the deposition chamber.
[0020] The provided method however raises the following issues:
[0021] the poor properties of PE-CVD for 3D deposition; [0022] the
evaporation of the precursors by bubbling: [0023] difficult control
of the gas flow rates sent into the deposition chamber, which
generates problems of reproducibility in terms of thickness and/or
of layer composition; [0024] heating of all the "precursor" source
strongly limiting the selection of organometallic precursors likely
to be used: most lithium-based organometallic materials tend to
form oligomers which are difficult to evaporate, and even to
decompose when the heating is extended, which results in a poor
evaporation efficiency; [0025] for precursors having a low vapor
pressure, such as lithium-based organometallic complexes, it is
extremely difficult or even impossible to generate vapor rates
sufficiently high to obtain films with high growth rates; [0026]
difficult control of the nitrogen rate due to the plasma
incorporation mode.
[0027] As a summary, such a vaporization process does not enable to
control the quantity of involved precursors. Further, it has a low
efficiency since it generates little vapor for a significant
quantity of initial matter.
[0028] There thus is an obvious need to develop new methods for
forming thin layers containing lithium which do not have the
above-mentioned disadvantages.
DISCUSSION OF THE INVENTION
[0029] In practice, the present invention thus aims at a method for
forming a lithium-based electrolyte for thin-film batteries on a 3D
substrate. This electrolyte may for example be LiPON, which
contains lithium (Li), phosphorus (P), oxygen (O), and nitrogen
(N).
[0030] As already mentioned, in such a context, the adapted
deposition technique is CVD. As a reminder, CVD is a method for
forming a thin layer on a surface when, by chemical reaction,
certain elements of a gaseous mixture placed in specific pressure
and temperature conditions pass from the vapor state to the solid
state by depositing on the material forming the surface. The CVD
may be plasma-enhanced (PE-CVD).
[0031] The main difficulty then is due to lithium (Li) since there
exist no lithium compounds in gas or liquid form at ambient
temperature, compatibles with CVD.
[0032] The only option available up to now is to use solid
precursors, as described in document US 2005/0016458.
[0033] The present invention provides a particularly appropriate
alternative solution which comprises going through an intermediate
liquid phase. It is indeed easier to vaporize a liquid than a
solid. More specifically, the present invention relates to a method
for forming by CVD a lithium-based layer, according to which the
lithium precursor is in liquid form in a mixture containing a Lewis
base.
[0034] According to a preferred embodiment, the method according to
the invention thus uses a liquid mixture comprising at least a
lithium precursor, a Lewis base, and a solvent.
[0035] In other words, the liquid medium comprises at least three
distinct entities, that is, the lithium precursor, a solvent, and a
Lewis base. It should be noted that in certain cases, a same
molecule may perform two of these functions (for example, solvent
and Lewis base or lithium precursor and Lewis base) but that the
invention provides the intentional addition of a Lewis base,
advantageously as defined hereafter, in addition to the precursor
and to the solvent normally used.
[0036] According to the principle of CVD, this liquid mixture is
then sprayed in the form of an aerosol, and then evaporated.
[0037] Preferably, the layer is made of a material selected from
the following group: [0038] LiPON; [0039] LiSiPON; and [0040]
(Li,La)TiO.sub.3.
[0041] As mentioned, lithium precursors are poorly soluble or
unstable in solution. Indeed, lithium (Li) is a chemical element
belonging to the first column of the periodic table of elements.
Such elements, called alkaline, are generally strongly
electropositive, thus mainly resulting in the forming of complexes
with strong ionicities.
[0042] In practice, the lithium precursors used in CVD, that is,
lithium-based organometallic compounds, appear in the form of solid
oligomers. Now, such solid oligomers generally have low vapor
pressures and poor properties of solubility in solvents
conventionally used for the dissolving of organometallic precursors
(called "usual").
[0043] The solution provided in the context of the present
invention thus is to use a solvent and a Lewis base for dissolving
the lithium precursor. By entering the coordination sphere close to
the metal center, the Lewis base breaks the polymer structure of
the oligomer, thus promoting the forming and the stabilization of
dimer, or even monomer structures.
[0044] The chemical compounds thus formed, called "adducts", most
often have higher vapor pressures, an increased solubility in
conventional aliphatic and/or aromatic organic solvents, as well as
an increased thermal stability of gas-phase precursors (during the
phase of vapor transport between the evaporation and the deposition
chamber) but also an increased chemical stability in liquid phase
(during the phase of precursor storage in the source
reservoirs).
[0045] Further, in the specific case where the Lewis base is an
amine, a potential nitrogen source enabling to dope the layer to be
synthesized is introduced into the coordination sphere close to the
metal element, and this, in a single step.
[0046] Thus, and advantageously, the Lewis base, present in the
liquid mixture, further containing the lithium precursor and the
solvent, is an amine, and more advantageously still: [0047] TMEDA
(N,N,N',N'-tetramethylethylenediamine); or [0048] TMPDA
(N,N,2,2-tetramethyl-1,3-propanediamine).
[0049] More specifically, the amine Lewis base may be primary
(R--NH.sub.2), secondary (R.sub.2--NH), or tertiary (NR.sub.3),
with R.dbd.CH.sub.3, C.sub.2H.sub.5, C.sub.3H.sub.7,
C.sub.4H.sub.9, or a combination of these groups in the case of
secondary and/or tertiary amines.
[0050] The amine Lewis base may be monodentate, as previously
mentioned, or more advantageously bidentate (diamine) of type
R.sub.2N--(CH.sub.2).sub.x--NR.sub.2 with x=1, 2, 3 or 4 and
R.dbd.CH.sub.3, C.sub.2H.sub.5, C.sub.3H.sub.7, C.sub.4H.sub.9 or a
combination of these groups.
[0051] Finally, the Lewis base may be an oxygenated compound of
(R--O--R) ether type, with R.dbd.CH.sub.3, C.sub.2H.sub.5,
C.sub.3H.sub.7, C.sub.4H.sub.9 or a combination of these
groups.
[0052] Again, the oxygenated Lewis base may be monodentate, as
previously mentioned (R--O--R), or more advantageously bidentate
(Glyme x) of type R--O--(CH.sub.2).sub.x--O--R with x=1, 2, 3, or 4
and R.dbd.CH.sub.3, C.sub.2H.sub.5, C.sub.3H.sub.7, C.sub.4H.sub.9
or a combination of these groups.
[0053] As a variation, the Lewis base may be acetylacetone or
benzylic alcohol.
[0054] A mixture of Lewis bases may of course be used.
[0055] As already mentioned, the use of an adequately selected
Lewis base in association with the precursor will provide: [0056] a
chemical stabilization of the precursor in solution in the source
reservoir, [0057] an increase of the solubility thereof in
conventional aliphatic and/or aromatic organic solvents, [0058] a
stabilization of the molecular structure of the precursor during
the transport phase in the form of gas between the evaporator and
the deposition chamber of the CVD reactor.
[0059] Preferably, the lithium precursor is a omanometallic
precursor, advantageously an alkoxide, such as for example lithium
tert-butoxide (LiO.sup.tBu), or a .beta.-diketonate, such as
lithium acetylacetonate (LiAcac) and/or lithium
2,2,6,6-tetramethyl-3-5-heptanedionate (LiTMHD), or an amide such
as lithium Bis-trimethylsilylamidure (LiHMDS). It may of course be
a mixture of lithium precursors.
[0060] The placing in liquid solution of the lithium precursor, in
the presence of a Lewis base, is advantageously achieved by means
of an aliphatic organic solvent of empirical formula
C.sub.xH.sub.2x+2 with x=3, 4 , 5, 6, 7, 8, or 9, or a
non-oxygenated aromatic solvent such as benzene, toluene, xylene,
mesitylene . . . , or an oxygenated organic solvent of alcohol
type, such as butanol or isopropanol. Monoglyme also is a possible
solvent. It may be a mixture of solvents.
[0061] Conversely to prior art where the lithium precursor was
provided in solid form, the present invention provides vaporizing a
lithium precursor present in liquid form. Of course, if the lithium
precursor is not liquid, it may have a solid initial form. Its
placing in solution by means of at least one solvent and one Lewis
base then forms an intermediate step before its vaporizing.
[0062] In the liquid mixture, the molar concentration of the Lewis
base generally is from 1 to 20 times greater than that of the
lithium precursor. The Li concentration may advantageously range
between 0.01 M and 1 M.
[0063] As already mentioned, the layer, especially the electrolyte,
may contain elements other than lithium (Li), in particular
phosphorus (P), nitrogen (N), oxygen (0), silicon (Si), titanium
(Ti), or lanthanum (La). These elements may be introduced by means
of the lithium precursor, or possibly via other precursors.
[0064] In a preferred embodiment, these other elements, especially
phosphorus and/or nitrogen, are also introduced in liquid form.
These advantageously are organometallic precursors in solution or
in the form of pure liquids. In this case, the liquid mixture then
contains, in addition to the lithium precursor, the Lewis base and
the solvent, at least another organometallic precursor.
[0065] For phosphorus, phosphate-based solutions, such as triphenyl
phosphate (TPPa) or trimethyl phosphate (TMPa), as well as
phosphite-based solutions, for example, triphenyl phosphite (TPPi)
or trimethyl phosphite (TMPi), may be used. The concentration of
the solutions advantageously ranges between 0.01 M and 1 M.
[0066] The Ti precursor may be an alkoxyde or .beta.-diketonate or
oxo-.beta.-diketonate (for example, TiO(Acac).sub.2) ou
alcoxo-.beta.-diketonate (for example Ti(OR).sub.2(TMHD).sub.2).
The La precursor may be a complexed or not .beta.-diketonate (for
example, La(TMHD).sub.3) or its adduct (for example,
La(TMHD).sub.3tetraglyme).
[0067] The different precursors may be prepared or introduced into
different solutions or mixtures, in particular two, for example,
one containing Li+N and the other containing P. As a variation, all
precursors are in the same mixture (for example, Li+P+N), which
thereby also contains the Lewis base and the solvent. As already
mentioned, the nitrogen source may be formed by the Lewis base.
[0068] Conventionally, the method according to the invention is
performed in a CVD-type deposition reactor. It may be carried out
at low pressure as well as at the atmospheric pressure.
[0069] At the atmospheric pressure, the method comprises the steps
of: [0070] introduction of the precursors: spraying in the form of
an aerosol. The aerosol may be generated either by a piezoelectric
ceramic, or by a system of spraying nozzle type, or via
automobile-type liquid injectors; [0071] transfer of the aerosol to
the deposition chamber by a duct having a carrier gas injected
therein (Ar, O.sub.2, N.sub.2, air); [0072] evaporation of the
precursors close to the surface of the heated substrate; [0073]
reaction at the surface of the heated substrate (possibility of
injecting reactive gases into the deposition chamber). The
substrate may be heated between 200 and 700.degree. C.
[0074] At low pressure, the method comprises the steps of: [0075]
introduction of the precursors: spraying via automobile-type liquid
injectors, followed by an evaporation in an evaporator; [0076]
transfer of the gas mixture to the deposition chamber through a
heated duct; [0077] reaction at the surface of the heated
substrate. Possibility of injecting reactive gases into the
deposition chamber: O.sub.2, N.sub.2O, H.sub.2, NH.sub.3 . . . The
pressure in the chamber is fixed. It ranges between 0.1 mbar and
500 mbar. The substrate temperature ranges between 200 and
800.degree. C., advantageously between 300 and 500.degree. C.
[0078] In both cases, the precursor flow rates are carefully
controlled. The deposition rates may exceed 750 nm/h.
[0079] As already mentioned, especially in the preferred
application relative to electrolytes for microbatteries, the method
according to the invention advantageously enables to form layers on
3D textured structures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0080] The way in which the invention may be implemented and the
resulting advantages will better appear from the following
non-limiting embodiments, in relation with the accompanying
drawings, among which:
[0081] FIG. 1 illustrates the spectroscopy impedance measurement
enabling to calculate the ion conductivity of a deposition
performed at the atmospheric pressure, by means of the method
according to the invention.
[0082] FIG. 2 illustrates an SEM (scanning electronic microscopy)
image of a deposition performed on a 3D substrate at the
atmospheric pressure, by means of the method according to the
invention.
[0083] FIG. 3 illustrates the spectroscopy impedance measurement
enabling to calculate the ion conductivity of a deposition
performed at low pressure, by means of the method according to the
invention.
[0084] FIG. 4 illustrates an SEM (scanning electronic microscopy)
image of a deposition performed on a 3D substrate at low pressure,
by means of the method according to the invention.
EMBODIMENTS OF THE INVENTION
I/Preparation of a Lipon Layer
[0085] I-1/Embodiment at the Atmospheric Pressure:
[0086] A mixture of LiAcac or LiTMHD and TPPa is used at
concentrations ranging between 0.03 M and 0.12 M. The solvent used
is butanol or toluene by adding, as a Lewis base, acetylacetone or
benzylic alcohol or TMEDA, or a mixture thereof (with a molar
concentration ranging between 1 and 20 times that of the lithium
precursor).
[0087] The deposition rates vary between 50 and 300 nm/h, with
temperatures of the substrate carrier ranging between 400 and
550.degree. C.
[0088] The curve of FIG. 1 enables to calculate the ion
conductivity of this material: 2.10.sup.-8 S/cm.
[0089] The conformality of the deposition is greater than 70% for
high shape factors (1:5) (FIG. 2).
[0090] The composition measured by XPS is
Li.sub.2.54PO.sub.3.97N.sub.0.19. The variation of the precursor
concentrations varies ratios x, y, and z of the LiPON layer
(Li.sub.xPO.sub.yN.sub.z).
[0091] I-2/Low Pressure Embodiment:
[0092] The mixture of precursors used in this case is LiO.sup.tBu
and TMEDA and TPPa. The concentration of the Li precursor solution
is 0.1 M and that of phosphorus is 0.03 M. The TMEDA (Lewis base)
concentration is approximately 10 times greater than that of
LiO.sup.tBu. The temperature of the substrate carrier ranges
between 420 and 480.degree. C., the oxygen proportion varies from
25% to 60%. The working pressure ranges between 10 and 20 mbar.
[0093] The deposition rates range between 220 and 980 nm/h.
[0094] The electric properties show an ion conductivity of
2.10.sup.-9 S/cm and an electronic conductivity <7.10.sup.-14
S/cm (FIG. 3).
[0095] The conformality of the deposition on significant shape
factors (1:5) is 56% (FIG. 4).
[0096] XPS and EDX analyses show the forming of a
Li.sub.xPO.sub.yN.sub.z layer.
II/Other Materials
[0097] II-1/LiSiPON at Low Pressure:
[0098] A mixture formed of: [0099] Bis-trimethylsilylamide
Li(hmds), [0100] TMEDA, and [0101] TPPa is used at concentrations
ranging between 0.03 M and 0.1 M.
[0102] The temperature of the substrate carrier ranges between 400
and 600.degree. C., the oxygen proportion varies from 25 to
70.degree. C. The work pressure ranges between 10 and 25 mbar.
[0103] The deposition rates range between 100 and 400 nm/h.
[0104] II-2/(Li,La)TiO.sub.3 at the Atmospheric Pressure
[0105] A mixture of LiAcac or LiTMHD, and of Ti precursor such as
alkoxyde or .beta.-diketonate or oxo-.beta.-diketonate (for
example, TiO(Acac).sub.2) or alcoxo-.beta.-diketonate (for example,
Ti(OR).sub.2(TMHD).sub.2), and of La precursor such as
.beta.-diketonate, complexed or not (for example, La(TMHD).sub.3)
or its adduct (for example La(TMHD).sub.3tetraglyme), is used at
concentrations ranging between 0.01 M and 0.1 M. The solvent used
is butanol or toluene by adding acetylacetone or benzylic alcohol
or TMEDA, or a mixture thereof (with a molar concentration ranging
between 1 and 20 times that of the lithium precursor).
[0106] The deposition rates vary between 50 and 500 nm/h, with
temperatures of the substrate carrier ranging between 400 and
650.degree. C.
[0107] II-3/(Li,La)TiO.sub.3 at Low Pressure:
[0108] A mixture of LiTMHD and of Ti(OiPr).sub.2(TMHD).sub.7 and
La(TMHD).sub.3 is used at concentrations ranging between 0.01 M and
0.1 M. The solvent used is monoglyme by adding TMEDA (with a molar
concentration ranging between 1 and 20 times that of the lithium
precursor).
[0109] The deposition rates vary between 50 and 500 nm/h, with
temperatures of the substrate carrier ranging between 400 and
800.degree. C., preferably between 500 and 650.degree. C.
* * * * *